Piezoresistor

Abstract

The invention relates to the technical field of circuit protection devices, in particular to a piezoresistor which comprises a packaging structure, a first pin, a second pin, a PTC thermistor unit and a piezoresistor unit, the PTC thermistor unit and the piezoresistor unit are packaged in the packaging structure, the second pin is electrically connected with the piezoresistor unit, and the first pin and the second pin are both partially exposed out of the packaging structure. The PTC thermistor unit comprises a PTC thermistor ceramic cavity, a first conductive part, a second conductive part and a bimetal reed, the first conductive part and the second conductive part are electrically connected with the two opening ends of the PTC thermistor ceramic cavity respectively and define a mounting cavity, and the bimetal reed is arranged in the mounting cavity; one end of the bimetal reed is fixedly and electrically connected with one of the first conductive piece and the second conductive piece, the other end of the bimetal reed is used as a movable contact to abut against the other one of the first conductive piece and the second conductive piece, the first conductive piece is electrically connected with the first pin, and the second conductive piece is electrically connected with the piezoresistor. The device is high in reliability and simple in structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit protection devices, in particular to a pressure sensitive resistor. BACKGROUND

[0002] The pressure sensitive resistor has high impedance, small leakage current and is in an open circuit state when the circuit voltage is normal, and when facing high surge voltage, the resistance of the pressure sensitive resistor drops instantaneously to discharge large current to provide protection to the subsequent circuit with low residual voltage.

[0003] The pressure sensitive resistor will deteriorate and fail due to continuous voltage impact during long-term use, which can easily cause fire accidents and other safety accidents, and there is a safety hazard. Therefore, the manufacturers of the pressure sensitive resistor have designed various safety measures, such as pressure sensitive resistors with thermal tripping devices, overcurrent devices, thermal melting current devices and explosion-proof devices, but these pressure sensitive resistors have complex structures or are prone to false triggering, resulting in low reliability.

[0004] Therefore, it is necessary to design a pressure sensitive resistor with a simple structure and high reliability. SUMMARY

[0005] The embodiments of the present application provide a pressure sensitive resistor to solve the problem of complex structure and low reliability of the existing pressure sensitive resistor with safety measures.

[0006] The present application discloses a pressure sensitive resistor, comprising a packaging structure, a first pin, a second pin, and a PTC thermistor unit and a pressure sensitive resistor unit packaged in the packaging structure, the second pin is electrically connected with the pressure sensitive resistor unit, the first pin and the second pin are partially exposed outside the packaging structure, the PTC thermistor unit comprises a PTC thermistor ceramic cavity with two open ends, a first conductive part, a second conductive part and a bimetallic spring, the first conductive part and the second conductive part are respectively electrically connected with the two open ends of the PTC thermistor ceramic cavity and form an installation cavity, the bimetallic spring is arranged in the installation cavity, one end of the bimetallic spring is fixedly and electrically connected with one of the first conductive part and the second conductive part, and the other end of the bimetallic spring is arranged as a moving contact and abuts against the other one of the first conductive part and the second conductive part, the first conductive part extends out of the first pin outside the packaging structure, and the second conductive part is electrically connected with the pressure sensitive resistor, wherein, when the temperature is greater than or equal to a preset temperature, the bimetallic spring deforms to disconnect the moving contact of the bimetallic spring from the corresponding first conductive part or second conductive part, and when the temperature is less than the preset temperature, the bimetallic spring restores the deformation to electrically connect the moving contact of the bimetallic spring with the corresponding first conductive part or second conductive part.

[0007] Optionally, the PTC thermistor unit comprises a first electrode layer and a second electrode layer, and the PTC thermistor further comprises a third pin, the second conductive member is electrically connected with the first electrode layer and extends out of the packaging structure to form the third pin, and the second electrode layer is electrically connected with the second pin.

[0008] Optionally, the PTC thermistor unit comprises a PTC chip, first and second electrode layers are respectively arranged on opposite end surfaces of the PTC chip, the second conductive member is welded on the first electrode layer, and the second pin is electrically connected with the second electrode layer.

[0009] Optionally, the bimetallic spring comprises a first bent extension, a transition connecting portion and a second bent extension, the transition connecting portion is obliquely arranged in the mounting cavity, the first bent extension and the second bent extension are respectively arranged at two ends of the transition connecting portion, the first bent extension serves as a moving contact of the bimetallic spring and abuts against one of the first conductive member and the second conductive member, and the second bent extension is fixedly and electrically connected with the other of the first conductive member and the second conductive member.

[0010] Optionally, the first conductive member is in a sheet shape, and a portion of the first conductive member located in the packaging structure covers one of the open ends of the PTC thermistor ceramic cavity.

[0011] Optionally, the second conductive member is in a sheet shape, and a portion of the second conductive member located in the packaging structure covers the other open end of the PTC thermistor ceramic cavity.

[0012] Optionally, the packaging structure comprises a packaging shell wrapped around the outer periphery of the PTC thermistor unit and the PTC thermistor unit.

[0013] Optionally, the packaging structure comprises a coating layer wrapped around the outer periphery of the PTC thermistor unit and the PTC thermistor unit.

[0014] Optionally, the PTC thermistor ceramic cavity is respectively provided with a third electrode layer and a fourth electrode layer at two open ends thereof, the first conductive member is welded on the third electrode layer, and the second conductive member is welded on the fourth electrode layer.

[0015] Optionally, the first conductive member is adhered to the third electrode layer by conductive adhesive, and the second conductive member is adhered to the fourth electrode layer by conductive adhesive.

[0016] The pressure sensitive resistor provided by the embodiment of the present application has the advantages that: by packaging the PTC thermistor unit and the pressure sensitive resistor unit in a packaging structure, and connecting to the applied circuit through the first pin and the second pin, the second conductive part of the PTC thermistor unit is electrically connected with the pressure sensitive resistor unit, when the pressure sensitive resistor unit is in the early stage of deterioration failure, the sustained temperature of the bimetallic spring of the pressure sensitive resistor unit coupled to the PTC thermistor unit exceeds the preset temperature, so that the bimetallic spring is deformed to disconnect the movable contact thereof from the corresponding first conductive part or second conductive part, thereby connecting the first conductive part and the second conductive part of the PTC thermistor unit in series with the pressure sensitive resistor unit, the PTC thermistor unit rapidly enters the high resistance state under the joint action of heat and current, the balance temperature of the PTC thermistor unit in the high resistance state continues to maintain the high temperature deformation state of the bimetallic spring in the mounting cavity, the PTC thermistor unit remains in the high resistance state, so that the failed pressure sensitive resistor unit is disconnected from the electrical connection with the applied circuit, the safety hidden danger caused by the failure of the pressure sensitive resistor unit is reduced, the reliability is high, and the structure is relatively simple. BRIEF DESCRIPTION OF DRAWINGS

[0017] The technical solutions of the present application will be further described in detail below with reference to the drawings and embodiments, and the drawings are as follows: Figure 1 is the internal structure schematic diagram of the pressure sensitive resistor of the embodiment of the present application; Figure 2 is the plane structure schematic diagram of the bimetallic spring of the embodiment of the present application.

[0018] The various reference signs in the drawings are as follows: 10, packaging structure; 11, coating layer; 20, first pin; 30, second pin; 40, PTC thermistor unit; 40a, mounting cavity; 41, PTC thermistor ceramic cavity; 43, first conductive part; 44, second conductive part; 45, bimetallic spring; 451, first bending extension; 452, transition connection part; 453, second bending extension; 50, pressure sensitive resistor unit; 51, pressure sensitive chip; 52, first electrode layer; 53, second electrode layer; 60, third pin. DETAILED DESCRIPTION

[0019] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The preferred embodiments of the present application will be described in detail with reference to the drawings.

[0020] The voltage-sensitive nonlinear resistor is a voltage-sensitive nonlinear resistor, whose resistance value changes exponentially with the applied voltage, and has a bidirectional symmetric volt-ampere characteristic. When the circuit voltage is normal, the voltage-sensitive nonlinear resistor has extremely high impedance and extremely small leakage current, and is in an approximate open circuit state. When facing high surge voltage, the resistance of the voltage-sensitive nonlinear resistor instantaneously drops to discharge large current to provide protection to the subsequent circuit with a low residual voltage. The voltage-sensitive nonlinear resistor may fail due to aging during long-term use, and such failure may be accompanied by serious safety accidents such as fire.

[0021] In different application sites, the higher the voltage-sensitive voltage is, the higher the reliability of the voltage-sensitive nonlinear resistor itself is. However, the high residual voltage caused by the voltage-sensitive nonlinear resistor with high voltage-sensitive voltage is not very friendly to the protected object. The voltage-sensitive nonlinear resistor with low voltage-sensitive voltage protects the protected object with low residual voltage, but the fault rate may cause various safety hazards. Although the voltage-sensitive nonlinear resistor manufacturers design various safety measures, such as voltage-sensitive nonlinear resistors with thermal tripping devices, overcurrent devices, thermal melting current devices, or explosion-proof devices. However, these voltage-sensitive nonlinear resistors have complex structures, are prone to false triggering, have low reliability, or are not easy to operate.

[0022] The embodiment of the present application provides a voltage-sensitive nonlinear resistor with high reliability and simple structure.

[0023] As shown in Figure 1 The voltage-sensitive nonlinear resistor provided by the embodiment of the present application includes a packaging structure 10, a first pin 20, a second pin 30, and a PTC thermistor unit 40 and a voltage-sensitive nonlinear resistor unit 50 packaged in the packaging structure 10. The second pin 30 is electrically connected with the voltage-sensitive nonlinear resistor unit 50. The first pin 20 and the second pin 30 are partially exposed outside the packaging structure 10. The PTC thermistor unit 40 includes a PTC thermistor ceramic cavity 41 with two open ends, a first conductive member 43, a second conductive member 44, and a bimetallic spring 45. The first conductive member 43 and the second conductive member 44 are respectively electrically connected with the two open ends of the PTC thermistor ceramic cavity 41 and form an installation cavity 40a. The bimetallic spring 45 is arranged in the installation cavity 40a. One end of the bimetallic spring 45 is fixedly and electrically connected with one of the first conductive member 43 and the second conductive member 44, and the other end thereof serves as a moving contact and abuts against the other one of the first conductive member 43 and the second conductive member 44. The first conductive member 43 extends out of the first pin 20 outside the packaging structure. The second conductive member 44 is electrically connected with the voltage-sensitive nonlinear resistor. When the temperature is greater than or equal to a preset temperature, the bimetallic spring 45 deforms to disconnect the moving contact thereof from the corresponding first conductive member 43 or second conductive member 44. When the temperature is less than the preset temperature, the bimetallic spring 45 restores the deformation to electrically connect the moving contact thereof with the corresponding first conductive member 43 or second conductive member 44.

[0024] The PTC thermistor unit 40 and the pressure sensitive resistor unit 50 are packaged in the packaging structure 10, and can be connected to the applied circuit through the first pin 20 and the second pin 30, the second conductive part 44 of the PTC thermistor unit 40 is electrically connected with the pressure sensitive resistor unit 50, when the pressure sensitive resistor unit 50 is in the early stage of deterioration failure, the sustained temperature of the bimetallic spring 45 of the pressure sensitive resistor unit 50 coupled to the PTC thermistor unit 40 exceeds the preset temperature, so that the bimetallic spring 45 generates deformation to make the movable contact thereof disconnected with the corresponding first conductive part 43 or the second conductive part 44, thereby connecting the PTC thermistor unit 40 in series with the pressure sensitive resistor unit 50 through the first conductive part 43 and the second conductive part 44, the PTC thermistor unit 40 rapidly enters the high resistance state under the joint action of heat and current, the balance temperature of the PTC thermistor unit 40 in the high resistance state continues to maintain the high temperature deformation state of the bimetallic spring 45 in the mounting cavity, the PTC thermistor unit 40 remains in the high resistance state, thereby disconnecting the failed pressure sensitive resistor unit 50 from the electrical connection with the applied circuit, reducing the safety hazard caused by the failure of the pressure sensitive resistor unit 50, having higher reliability, and the structure is relatively simple.

[0025] The bimetallic spring 45 can be fixedly electrically connected with the first conductive part 43, and the movable contact thereof abuts against the second conductive part 44, or the bimetallic spring 45 can be fixedly electrically connected with the second conductive part 44, and the movable contact thereof abuts against the first conductive part 43, and the conductive part abutting against the bimetallic spring 45 serves as the fixed contact. For example, the bimetallic spring 45 is fixedly electrically connected with the second conductive part 44, and the movable contact thereof abuts against the first conductive part 43, and the second conductive part 44 fixedly electrically connected with the bimetallic spring 45 is electrically connected with the pressure sensitive resistor unit 50, thereby forming more reliable thermal coupling while forming reliable electrical connection with the pressure sensitive resistor unit 50, and facilitating the coupling of heat, and transmitting the abnormal heat of the pressure sensitive resistor unit 50 to the bimetallic spring 45 of the PTC thermistor unit 40.

[0026] The bimetallic spring 45 is fixedly electrically connected with the corresponding conductive part, and can be welded and assembled on the corresponding conductive part by spot welding to form reliable electrical connection with the corresponding conductive part. The bimetallic spring 45 is laminated and combined by two or more metal layers with different thermal expansion coefficients, and the core feature is that the bimetallic spring 45 is bent due to the deformation difference of each layer when the temperature changes, and the movable contact of the bimetallic spring 45 also has a certain resistivity, and can also generate a certain heat when a certain large current flows, thereby accelerating the generation of such deformation.

[0027] The PTC thermistor ceramic cavity 41 is mainly made of barium carbonate and titanium dioxide, and has different Curie temperatures according to different formulations. The PTC thermistor unit 40 will quickly enter a high resistance state under the maximum working voltage. The surface temperature of the PTC thermistor unit 40 in the high resistance state is called the equilibrium temperature, which is about 30-40℃ higher than the Curie temperature. The equilibrium temperature changes little within the normal working voltage fluctuation range after the PTC thermistor protection, and the equilibrium temperature can just maintain the open state of the moving contact of the bimetallic spring 45 and the conductive part as the static contact.

[0028] The PTC thermistor ceramic cavity 41 can have various shapes, which are not specifically limited here.

[0029] In the optional embodiment of the present application, the first conductive part 43 and the second conductive part 44 are in the form of a sheet. The part of the first conductive part 43 located in the packaging structure 10 fits to cover one of the open ends of the PTC thermistor ceramic cavity 41. The part of the second conductive part 44 located in the packaging structure 41 fits to cover the other open end of the PTC thermistor ceramic cavity 41. The first conductive part 43 and the second conductive part 44 can better disperse the heat generated by current conduction. When the circuit is working normally, the current is distributed more evenly through the sheet-shaped first conductive part 43 and the second conductive part 44, which is conducive to maintaining the temperature stability of the PTC thermistor unit. When the circuit fails and the temperature rises to the preset temperature or above, the bimetallic spring 45 deforms, and the moving contact of the bimetallic spring 45 separates from the sheet-shaped second conductive part 44. Since the surface of the sheet-shaped second conductive part 44 is flat, the disconnection action can be more reliable. When the temperature returns to below the preset temperature, the moving contact of the bimetallic spring 45 can more accurately abut against the sheet-shaped second conductive part 44, ensuring the smooth conduction of the circuit. The part of the first conductive part 43 located in the packaging structure 10 fits to cover one of the open ends of the PTC thermistor ceramic cavity 41, which can make the first conductive part 43 smaller in size after being electrically connected to the PTC thermistor ceramic cavity 41. Similarly, the part of the second conductive part 44 located in the packaging structure 10 fits to cover the other open end of the PTC thermistor ceramic cavity 41, which can make the second conductive part 44 smaller in size after being electrically connected to the PTC thermistor ceramic cavity 41.

[0030] Reference Figure 1In an alternative embodiment of the present application, the piezoresistance unit 50 comprises a first electrode layer 52 and a second electrode layer 53, and the piezoresistor further comprises a third pin 60, the second conductive member 44 is electrically connected with the first electrode layer 52 and extends out of the package structure 10 to form the third pin 60, and the second electrode layer 53 is electrically connected with the second pin 30. The third pin 60 can be used to connect to an audible and light alarm circuit, and in the case of overvoltage, the piezoresistance unit 50 will have a switching signal transmitted to the related circuit to trigger the alarm action, thereby providing a proper audible and light alarm indication for the failure of the piezoresistance unit 50. The audible and light alarm circuit can be a conventional circuit using a buzzer, an LED lamp, etc., which will not be described herein.

[0031] Reference Figure 1 In an alternative embodiment of the present application, the piezoresistance unit 50 comprises a piezoresistance chip 51, and the first electrode layer 52 and the second electrode layer 53 are respectively arranged on opposite end faces of the piezoresistance chip 51, the second conductive member 44 is welded on the first electrode layer 52, and the second pin is electrically connected with the second electrode layer 53.

[0032] Specifically, the first electrode layer 52 and the second electrode layer 53 are respectively arranged on opposite end faces of the piezoresistance chip 51, which can provide a larger contact area for electrical connection with the second conductive member 44 and the second pin 30. The second conductive member 44 is welded on the first electrode layer 52, which can ensure more reliable electrical connection and heat coupling.

[0033] In the present application, the first electrode layer 52 and the second electrode layer 53 can be formed on the first end face and the second end face of the piezoresistance chip 51 by printing, and are electrically connected with the piezoresistance chip 51.

[0034] It should be noted that the core material of the piezoresistance chip 51 is metal oxide such as zinc oxide, and the resistance value of the piezoresistance chip 51 changes exponentially with the applied voltage.

[0035] Reference Figure 1 and Figure 2In the optional embodiment of the present application, the bimetallic spring 45 includes a first bent extension 451, a transition connection portion 452, and a second bent extension 453. The transition connection portion 452 is obliquely arranged in the mounting cavity. The first bent extension 451 and the second bent extension 453 are respectively arranged at two ends of the transition connection portion 452. The first bent extension 451, as a movable contact of the bimetallic spring 45, abuts against one of the first conductive member 43 and the second conductive member 44. The second bent extension 453 is fixedly and electrically connected to the other one of the first conductive member 43 and the second conductive member 44. The oblique arrangement of the transition connection portion 452 can optimize the thermal response performance of the bimetallic spring 45. When the temperature reaches a preset temperature, the oblique transition connection portion 452 can more quickly respond to the temperature change to produce overall deformation. After the second bent extension 453 is fixedly connected to the corresponding conductive member, a stable support end is formed, which serves as a bracket of the bimetallic spring 45 to mount the bimetallic spring 45 in the mounting cavity 40a. The first bent extension 451 abuts against the corresponding conductive member in a natural state to form an electrical connection, thereby short-circuiting the first conductive member 43 and the second conductive member 44. At this time, the bimetallic spring 45 as a whole is in a slightly stressed balanced state. When the temperature change causes the bimetallic spring 45 to deform, this balance is broken. The change in the oblique angle of the transition connection portion 452 drives the movable contact to move about the corresponding conductive member as a fulcrum, so that the second bent extension 453 as the movable contact is disconnected from the electrical connection with the corresponding conductive member.

[0036] It should be noted that the designer can also adjust the thickness of the PTC thermistor ceramic cavity 41 to adjust the pressure of the movable contact and the corresponding conductive member to design the temperature at which the bimetallic spring 45 jumps, so as to meet the design requirements of different circuits for over-temperature protection temperature.

[0037] Reference Figure 1 In the optional embodiment of the present application, the PTC thermistor ceramic cavity 41 is respectively provided with a third electrode layer (not shown in the figure) and a fourth electrode layer (not shown in the figure) on the two open ends. The first conductive member 43 is welded to the third electrode layer of the PTC thermistor ceramic cavity 41, and the second conductive member 44 is welded to the fourth electrode layer of the PTC thermistor ceramic cavity 41.

[0038] Specifically, the first conductive member 43 and the second conductive member 44 are connected by welding the corresponding electrode layers of the PTC thermistor ceramic cavity 41, which can make the electrical connection between the first conductive member 43 and the second conductive member 44 and the PTC thermistor ceramic cavity 41 more firm, reduce problems such as heating and open circuit caused by poor connection, and ensure the stability of current conduction.

[0039] The third electrode layer and the fourth electrode layer on the PTC thermistor ceramic cavity 41 can be formed by printing.

[0040] In another optional embodiment of the present application, the first conductive member 43 is adhered to the third electrode layer of the PTC thermistor ceramic cavity 41 by conductive adhesive, and the second conductive member 44 is adhered to the fourth electrode layer of the PTC thermistor ceramic cavity 41 by conductive adhesive.

[0041] Specifically, the conductive adhesive operation is simple and does not require high-temperature welding. In terms of connection adaptability, the conductive adhesive has good wettability and filling property, and can fill the small gaps and uneven places between the first conductive member 43, the second conductive member 44 and the electrode layer of the PTC thermistor ceramic cavity 41, thereby ensuring close contact and reducing contact resistance. The conductive adhesive has certain elasticity and flexibility after solidification, can absorb external vibration and impact energy, and has high reliability. In addition, the chemical composition of the conductive adhesive is stable, and is not prone to oxidation, corrosion and other phenomena during long-term use, thereby ensuring long-term stability of the connection conductivity.

[0042] In an optional embodiment of the present application, the packaging structure 10 includes a packaging shell wrapped around the outer periphery of the PTC thermistor unit 40 and the varistor unit 50.

[0043] The packaging shell can provide a physical barrier for the PTC thermistor unit 40 and the varistor unit 50, effectively blocking the entry of external dust, water vapor, oil stains and other pollutants into the interior, thereby avoiding short circuit caused by contacting the internal connection circuit. In terms of mechanical protection, the packaging shell can buffer external mechanical impact and vibration. When the varistor is subjected to impact, falling or is in a vibrating environment, the packaging shell can absorb part of the energy, thereby reducing the direct force on the internal PTC thermistor unit and the varistor unit 50, avoiding damage to fragile or precision components such as the ceramic body and the bimetallic spring 45 due to mechanical stress, and enhancing the impact resistance of the overall structure.

[0044] In another optional embodiment of the present application, referring to Figure 1 , the packaging structure 10 includes a coating layer 11 wrapped around the outer periphery of the PTC thermistor unit 40 and the varistor unit 50.

[0045] The coating layer 11 is used as the packaging structure 10 of the PTC thermistor unit 40 and the varistor unit 50, and the coating layer 11 can be flexibly attached according to the specific structure and shape of the PTC thermistor unit 40 and the varistor unit 50, effectively isolating the internal components from the external environment and avoiding the phenomenon of electric leakage or short circuit. The thickness of the coating layer 11 can be accurately controlled, which is conducive to reducing the overall volume and weight of the varistor.

[0046] In the normal state of the application circuit, the leakage current flowing through the pressure sensitive resistor unit 50 is less than 20 microamperes, and the heat generated by the pressure sensitive resistor unit 50 can be ignored. In the process of absorbing the surge, the discharge current can reach 10 kiloamperes or more, and the temperature rise of the pressure sensitive resistor unit 50 under the transient current of microseconds can be absorbed by the heat capacity of the pressure sensitive resistor unit 50 and then slowly released to the outside through the surface. The heat coupled to the bimetallic spring 45 is limited. On the other hand, the heat generated by the micro-ohm internal resistance of the bimetallic spring 45 is also negligible. The above two factors will not cause the pressure sensitive resistor of the embodiment of the application to malfunction. When the pressure sensitive resistor unit 50 is in the early stage of deterioration and failure, the continuous temperature of the pressure sensitive resistor unit 50 coupled to the bimetallic spring 45 will exceed 100℃, and the continuous current flowing through the pressure sensitive resistor unit 50 will also exceed 100 amperes. This current will also generate a certain continuous power on the bimetallic spring 45, and when the two resonate, the deformation of the bimetallic spring 45 and the corresponding conductive part will be accelerated and disconnected. At the same time that the bimetallic spring 45 and the corresponding conductive part are disconnected, the PTC thermistor unit 40 in the low resistance state is connected. The PTC thermistor unit 40 in the low resistance state plays a role in arc extinguishing and explosion prevention in the seamless connection circuit, and at the same time, under the joint action of heat and current, it quickly enters the high resistance state. The equilibrium temperature of the PTC thermistor unit 40 in the high resistance state continues to maintain the high temperature deformation state of the bimetallic spring 45 in the installation cavity. The high resistance state of the PTC thermistor unit 40 is equivalent to an open circuit for the deteriorated and failed pressure sensitive resistor unit 50, which disconnects the failed pressure sensitive resistor unit 50 and reduces the safety hazard.

[0047] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent replacements to some technical features; all these modifications and replacements shall fall within the protection scope of the appended claims of the present application.

Claims

1. A varistor, characterized in that: The invention comprises a packaging structure, a first pin, a second pin, and a PTC thermistor unit and a varistor unit packaged in the packaging structure, wherein the second pin is electrically connected to the varistor unit, and the first pin and the second pin are partially exposed from the packaging structure. The PTC thermistor unit comprises a PTC thermistor ceramic cavity with two open ends, a first conductive member, a second conductive member, and a bimetallic spring. The first conductive member and the second conductive member are electrically connected to the two open ends of the PTC thermistor ceramic cavity, respectively, and enclosed to form an installation cavity. The bimetallic spring is arranged in the installation cavity, and the One end of the bimetallic spring is fixedly electrically connected to one of the first conductive member and the second conductive member, and the other end serves as a movable contact and abuts against the other of the first conductive member and the second conductive member. The first conductive member extends the first pin outside the package structure, and the second conductive member is electrically connected to the varistor. When the temperature is greater than or equal to a preset temperature, the bimetallic spring deforms to disconnect its movable contact from the corresponding first conductive member or the second conductive member. When the temperature is less than the preset temperature, the bimetallic spring recovers its deformation to electrically connect its movable contact to the corresponding first conductive member or the second conductive member.

2. The varistor according to claim 1, characterized in that The varistor unit includes a first electrode layer and a second electrode layer. The varistor also includes a third pin. The second conductive member is electrically connected to the first electrode layer and extends outside the packaging structure to form the third pin. The second electrode layer is electrically connected to the second pin.

3. The varistor according to claim 2, characterized in that The varistor unit includes a varistor chip, and a first electrode layer and a second electrode layer are respectively provided on opposite end surfaces of the varistor chip. The second conductive member is welded on the first electrode layer, and the second pin is electrically connected to the second electrode layer.

4. The varistor according to claim 1, wherein The bimetallic spring includes a first bent extension, a transition connection, and a second bent extension. The transition connection is obliquely arranged in the mounting cavity. The first bent extension and the second bent extension are respectively arranged at two ends of the transition connection. The first bent extension serves as a moving contact of the bimetallic spring and abuts against one of the first conductive member and the second conductive member. The second bent extension is fixedly electrically connected to the other of the first conductive member and the second conductive member.

5. The varistor according to claim 2, characterized in that The first conductive member is in a sheet shape, and a portion of the first conductive member located within the packaging structure is adapted to cover one of the opening ends of the PTC thermistor ceramic cavity.

6. The varistor according to claim 5, characterized in that The second conductive member is in a sheet shape, and a portion of the second conductive member located within the packaging structure is adapted to cover the other open end of the PTC thermistor ceramic cavity.

7. The varistor according to any one of claims 1 to 6, characterized in that: The packaging structure includes a packaging shell covering the outer circumference of the PTC thermistor unit and the varistor unit.

8. The varistor according to any one of claims 1 to 6, characterized in that: The packaging structure includes a coating layer covering the outer periphery of the PTC thermistor unit and the varistor unit.

9. The varistor according to any one of claims 1 to 6, characterized in that: A third electrode layer and a fourth electrode layer are respectively provided on the two open ends of the PTC thermistor ceramic cavity. The first conductive member is welded on the third electrode layer, and the second conductive member is welded on the fourth electrode layer.

10. The varistor according to claim 9, characterized in that The first conductive member is bonded to the third electrode layer by conductive adhesive, and the second conductive member is bonded to the fourth electrode layer by conductive adhesive.

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